The present invention relates to the detection of concealed current carrying conductors.
Detection systems for locating concealed current carrying conductors, such as buried electrical cables, are available. These available systems typically use two parallel, spaced coils to detect a magnetic field gradient of a current carrying conductor. In response to an alternating magnetic field, each coil develops an output signal. These output signals are processed separately using two analog signal processing channels. The signals generated by these two analog processing channels are compared and used to generate an audio signal that indicates to a system user whether a concealed current carrying conductor is present. See Lloyd Harold Sole, UK Patent Application GB 2,075,199, which is incorporated herein by reference in its entirety, for a more detailed description of how available detection systems operate.
While these available detection systems are able to local concealed current carrying conductors, they have limitations due to the circuitry used to process the output signals of the two coils. Such limitations include, for example, limited dynamic range, mistracking between the two analog processing channels due to the use of variable gain amplifiers, and gain drift with respect to time and temperature. These limitations, as well as other limitations, require that the available detections systems be periodically calibrated so that they will continue to operate as intended. Typically, these required calibrations must be performed manually using trimpots.
The limitations of the available detection systems such as, for example, gain drift result in inconsistent performance between two detection systems of identical make and model. Thus, there is a need for new systems and methods for detecting concealed current carrying conductors that do not suffer form the above limitations.
A system and method for detecting a concealed current carrying conductor is presented. A first and a second field strength signal proportional to an electromagnetic field is generated. A value is determined for the first field strength signal. This value is used to divide the second field strength signal and form an indicator signal. A value for the indicator signal is determined. If the value of the indicator signal is equal to or greater than a predetermined value (i.e., not less than the predetermined value), a conductor detection signal is generated and used to alert a user to the presence of a concealed current carrying conductor.
In an embodiment, the invention is implemented using a pair of parallel, spaced coils, a digital signal processing network, and an audible indicator network. In this embodiment, each coil generates an output signal proportional to a detected electromagnetic field. The output signal of each coil is digitally filtered and processed to determine whether an electromagnetic field gradient exists that is indicative of a concealed current carrying conductor. If a magnetic field gradient exists that is indicative of a concealed current carrying conductor, a conductor detection signal is generated and used to drive an audible indicator network.
In embodiments of the present invention, at least one of the first and the second field strength signals is adjusted to decrease the value of the indicator signal that is generated. Decreasing the value of the indicator signal reduces the detection system""s sensitivity to certain electromagnetic field gradients thereby enabling the detection system user to focus in on and pinpoint current carrying conductors that are closer to the detector system. In one embodiment, the first field strength signal is multiplied by a value greater than 1 to decrease the value of the indicator signal. In another embodiment, the second field strength signal is multiplied by a value between 0 and 1 to decrease the value of the indicator signal. In other embodiments, both the first and the second field strength signals are adjusted to decrease the value of the indicator signal.
As described herein, embodiments of the invention use an audible signal to alert the user of the invention to the presence of a concealed current carrying conductor. Other embodiments use a visual signal to alert the user of the invention to the presence of a concealed current carrying conductor. Still other embodiments use both an audible signal and a visual signal to alert the user of the invention to the presence of a concealed current carrying conductor.
There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.